I would love something like this. I agree that this information should be easily accessed from an individual soldier's screen, but I think some way to get an overview of the equipment state of the entire military is even more important - that way you would only have to check one screen instead of each soldier individually.
Shamelessly quoting myself here, something I wrote a while back in on of the "Return of the Guilds" threads:
However, one thing I'd really like is for the Captain to be able to give me a report on the current state of the forces.
Suppose I have three squads of 5 each - A, B and C. I order everyone in A to equip crossbows, leather armor and waterskins, everyone in B to equip axes, plate armor, backpacks and waterskins and everyone in C to fight unarmed in plate armor and with shields. The Captain would keep track of how his troops are supplied and would be able to tell me stuff like the following:
"15 dwarves are ordered to sleep in the barracks, but there are only 8 beds.
10 dwarves are ordered to carry water, but we only have 6 waterskins.
5 dwarves are ordered to use crossbows, but we only have 4 quivers.
5 dwarves are ordered to equip plate armor, but we only have 1 helm.
5 dwarves are ordered to equip plate armor, but we have no greaves.
We are running low on practice bolts, we only have 28 bolts left.
We have run out of rations."
This kind of smart reporting would help enormously when managing an army and would make it easy to figure out deficiencies and shortages. Furthermore, you should be able to specify "exceptional steel plate or better only" to stop dwarves carrying (turtle shell helm) and (bronze battle axe) and stuff like that. Or they could just be smart enough to upgrade their equipment on their own..
Even with something like this though, a quasi-graphical inventory display of individual dwarves' inventory would be pretty sweet.
Also: re-reading my post above, I realized there are some additional military gear the OP suggestion doesn't list, such as quiver, bedroll, waterskin, secondary weapon etc. I find myself checking my soldiers for these things as often as I check their armor, so perhaps they should be there as well.